We know that the size of atom is so small that it can not be seen with the most powerful microscope 🔬.
Then a doubt arises in our mind,how did scientists determined its structure?
They adopted a alternative method in which they will first studied the properties of an atom and on that basis they have determined its possible structure.
So always keep in mind that structure of an atom is determined on the basis of its properties but not by seeing it.
Retardation test (or) running 🏃 down test of dc machine
This method is used to find the constant losses(friction + windage + iron losses)
This is also a noload test. We can calculate the efficiency of a dc machine by knowing the armature amd shunt copper losses at a given load.
Consider a DC SHUNT MOTOR running at noload.
If the supply to the
1.Armature is cut off 📴 and the supply to the field remains same then the KINETIC ENERGY ⚡ is used to overcome (friction + Windage +Field copper ) no load losses
2.Armature as well as field to the field is cut off then the KINETIC ENERGY ⚡ is Used to overcome only the friction losses + Windage losses. (their will be no field copper loss because in second case their is no supply to the field)
How to conduct it:
It is very easy to conduct it we have to remove the supply and calculate the rate at which the speed falls.
Losses can be calculated by using formula (derivation):
Since kinetic energy ⚡ is used to overcome losses:
W=(d(Iw^2)/2dt)
where w(omega)= 2πN/60 in rad/sec
On differentiation we get
W= 2Iw (dw/dt)
Now substitute w= 2πN/60.
We get
W= (((2π)÷(60))^2)(IN(dN/dt))
Where
I=Moment of inertia of armature.
N=speed of armature in rpm.
Accordingly if the supply to the armature is cut off and supply to field is not cut off then 'W' indicates friction +windage+Field copper losses.
If supply to both armature as well as the field is Cut Off Then 'W' indicates only Friction + Windage Losses.
To find I:
But it is difficult to find the moment of inertia of Armature i.e 'I' . It can be easily found by conducting another experiment
Firstly,the retardation test is conducted and dN/dt1 is noted
Secondly,the shaft of the motor is keyed to the flywheel 🎡 of known moment of inertia I1 and the time for the fall of same speed is noted i.e dN/dt2
Since in both cases same motor is used so losses are equal
Losses in case1:
W= (((2π)÷(60))^2)(IN(dN/dt1))
Losses in case2:
W=(((2π)÷(60))^2)((I+I1)N(dN/dt2))
N=speed in rpm
I=Moment of inertia of armature.
I1=Moment of inertia of flywheel
Equating above two equations we get I value if I1 value is known
Hence by retardation test we can calculate losses.
The worlds largest electricity generating station is located in china.It is a hydro electric power plant which is across the dam THREE GORGES DAM. Its generating capacity in watts is 22500.
For generating that much amount of power it employs 32 Francis turbines each of a capacity of 700 MWand two 50 MW turbines.
32*700=22400 MW
02*50 = 100 MW
Total. =22500 MW
An 18th century scientist named ALESSANDRO VOLTA developed a voltaic pile which was later developed into battery 🔋.VOLTAGE is named after him.
It is one of multinational companies.It manufacturers airplanes and many other military equipments like missiles etc.,
It was sarted by WILLIAM E BOEING.He studied at YALE UNIVERSITY. He worked initally in a timber industry and he became wealthy and known about wooden structures.Slowly he built a seaplane and built ships. And it satarted to manufacture different types of planes which are used for wars.
Hai friends,
Please give one minute of your precious time and read this article.
Do you know one of cause for decrease in growth rate(the rate at which our height increases) in present generations is carrying weights.Many of the servays says that weight lifting affects the growth rate.Weight lifting decreases the growth rate or stops the growth. We may think that we are not carrying any weights it is obsoletely wrong but we have carried and even now every child is carrying a lot of weight daily .I mean from our nursery to 🔟 th class we have many books 📚 to carry.Every day we used to carry a lot of books 📚 from home 🏡 to school and from school to home.(CHILDHOOD IS THE MAJOR PART WHERE WE GROW MORE HEIGHT )
As I have already said that carrying weights decreases the growth rate.
So i want to make you aware about this and say to children 🚸 not carry books 📚 daily from home 🏡 to school 🏫 and from school 🏫 to home 🏡 instead they may keep their books in school.
I am not saying that if we doesn't carry books 📚 we will become height,but I am saying about a factor which affects our height.
You can take a live example:
Our parents and grandparents have also studied to some extent.Many of us are lesser in height compared to them it is because in their childhood they have very less books 📚.
Share this if you agree.
. 😊 M.CHAITANYA KUMAR REDDY
Two ✌ circuits are said to be duals of each other if cut set matrix of one circuit equal to the tieset matrix the later
